Configuration and racemization determination of cysteine residues in peptides by chiral derivatization and HPLC: application to oxytocin peptides.

An improved RP-HPLC method was developed for the determination of the configuration and stereochemical purity of cysteine residues in peptides. The method consists of oxidation of cysteine and cystine residues to cysteic acid, followed by hydrolysis and pre-column chiral derivatization with Val-Marfey's reagent.